The present invention relates to a fluid pump containing an encapsulated stator assembly that seals a pump motor and facilitates heat transfer from the motor and the electronics to the working fluid.
Use of fluid pumps in vehicle engine cooling systems and various industrial applications is well known. However, typical fluid pumps in both of these areas have inherent limitations.
Typically in engine cooling systems, a coolant pump has a pulley keyed to a shaft. The shaft is driven by the engine via a belt and pulley coupling, and rotates an impeller to pump the working fluid. Fluid seals sometimes fail due to the side load from the drive belt, which tends to allow fluid to leak past the seal into the bearing.
U.S. Pat. No. 6,056,518, issued on May 2, 2000 to Allen et al., describes one attempt to overcome the shortcomings of prior art vehicle coolant pumps. The ""518 patent provides a fluid pump with a switched reluctance motor that is secured to a housing and rotates an impeller for pumping the fluid. This design eliminates the side load problem associated with keyed pulleys, but it is generally not intended for use where larger industrial pumps are required.
Industrial pumps are typically driven by an electric motor connected to the pump via a coupling, the alignment of which is critical. Misalignment of the coupling can result in premature pump failure, which leads to the use of expensive constant velocity couplings to overcome this problem. Moreover, industrial pumps are typically air-cooled, relying on air from the surrounding environment. The cooling air is drawn through the motor leaving airborne dust and other contaminants deposited in the motor. These deposits can contaminate the bearings, causing them to fail, or the deposits can coat the windings, shielding them from the cooling air and causing the windings to overheat and short out.
Accordingly, it is desirable to provide an improved fluid pump which overcomes the above-referenced shortcomings of prior art fluid pumps, while also providing enhanced fluid flow rate and control capability while reducing costs.
The present invention provides a fluid pump with an encapsulated stator assembly that contains a rotor cavity. A rotor assembly, driven by a stator, is positioned within this cavity and turns an impeller for pumping the working fluid. The encapsulated stator assembly prevents the working fluid from directly contacting the motor. It does, however, have an outside wall that is in contact with the working fluid, thereby facilitating heat transfer from the motor to the fluid.
More specifically, the present invention provides a fluid pump including a housing having a housing cavity therein. An encapsulated stator assembly is positioned within the housing cavity and at least partially defines a boundary for the working fluid. The encapsulated stator assembly contains a rotor cavity in which a rotor assembly is located. The magnetic field generated by a stator drives the rotor assembly, which is connected to an impeller for pumping the fluid.
In a preferred embodiment, the encapsulated stator assembly is a single unit, and is located inside a two-piece housing. A stator comprising steel laminations, windings, and motor power leads, is encapsulated in a thermally conductive, electrically insulative polymeric capsule member. The polymeric capsule member defines a rotor cavity having an opening. The rotor assembly, consists of a rotor with a rotor shaft, the rotor shaft being supported by a front bearing and a rear bearing. Also, in the preferred embodiment, the rear bearing is located within the encapsulated stator assembly, and the front bearing and a seal are positioned within a front cover that plugs the rotor cavity opening.
A diffuser is used to help direct fluid flow and thereby increase the efficiency of the pump. The diffuser comprises an inner wall, an outer wall, and a plurality of diffuser vanes. The diffuser vanes are integrally molded to the outer wall of the encapsulated stator assembly. The polymeric capsule member orients the motor power leads with substantial circumferential symmetry around the diffuser. The motor power leads then interface with a circuit board assembly near the outlet of the pump. The working fluid flows around the outside of the encapsulated stator assembly, thereby encountering the diffuser vanes and allowing heat transfer from the motor to the fluid. The working fluid then encounters the encapsulated motor power leads, thereby cooling both the motor power leads and the circuit board assembly.
In an alternative embodiment, the one piece encapsulated stator assembly is replaced with a one piece stator housing assembly. This change allows for larger motors to be utilized with the pump, and thereby increases the number of applications in which the invention may be used. The stator housing assembly includes an encapsulated stator assembly and a substantially cylindrical metal case which provides an outlet for a single bundle of motor power leads and also contains diffuser vanes that fully define the boundary of the working fluid. The encapsulated stator assembly is enclosed and sealed by a thermally conductive, electrically insulative polymeric capsule member that defines a motor cavity and provides a heat transfer path to the working fluid. As in the preferred embodiment, a rotor with a rotor shaft is located in the motor cavity and is driven by the magnetic field generated by the stator. The motor housing assembly comprises a front cover, a stator housing assembly, and a rear cover.
This alternative embodiment also has a diffuser with diffuser walls and diffuser vanes; however, there are now two sets of diffuser vanes. The front cover is configured with a first set of diffuser vanes and the stator housing assembly is configured with a second set of diffuser vanes. The two covers and the stator housing assembly are joined together and sealed in a manner to prevent the working fluid from entering the motor cavity.
Accordingly, an object of the present invention is to provide a fluid pump with an encapsulated stator assembly, the encapsulated stator assembly orienting the motor components and providing heat transfer between the motor and the working fluid.
Another object of the invention is to provide a fluid pump with an encapsulated stator assembly, the encapsulated stator assembly forming a diffuser, including a plurality of diffuser vanes. The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.